Systematic studies of humoral and cellular immunity in patients with primary immunodeficiency syndromes are in progress, using bacteriophage phi X 174 as antigen to assess antibody formation, lymphocyte transformation to specific and nonspecific mitogens to assess cell function, rosette formation to differentiate T and B cells, and surface markers (immunoglobulin) to further identify lymphocyte sub-groups. Similar studies are also being carried out on patients with bone marrow transplants.